Cold cathode electron emitters include primarily field emission devices which originally required a very sharp tip to raise the field at the surface of the tip sufficiently to cause electrons to be drawn off, or emitted. Generally, an extraction electrode is formed in the plane of the tip and positioned to completely surround the tip to provide the extraction potential between the tip and the extraction electrode. The major problem with these devices is the difficulty in fabricating the very sharp tip. Further, once the tip is fabricated there is a tendency for the tip to degenerate, or lose particles, as the field emission device is operated.
To solve these problems, there has been a movement toward utilizing low work function material in the emitter. In some instances, such as utilizing a diamond emitter, the emitter can actually be constructed in a flat configuration while still providing a required amount of electron emission with the application of a reasonable potential. Examples of such structures are disclosed in U.S. Pat. No. 5,283,501, entitled "Electron Device Employing a Low/Negative Electron Affinity Electron Source", and assigned to the same assignee.
A problem also exists in these low work function devices in that there is too much extraction grid current. When a sharp tip is utilized, the emission is automatically at the center of the emitter and it is only necessary to focus the electron stream before it strikes an anode/screen. When a flat emitter is utilized, the electrons can be emitted from the surface anywhere in the field and, consequently, a large portion of the emitted electrons flow directly to the extraction electrode. The extraction electrode current greatly reduces the efficiency and operating characteristics of the device.
Accordingly, there exists a need for a flat cold cathode device which overcomes at least some of these shortcomings of the prior art.
It is one purpose of the present invention to provide a new and improved cold cathode electron emitter using patterned metal for electron emission control.
It is another purpose of the present invention to provide a new and improved cold cathode electron emitter in which extraction electrode current is substantially reduced.
It is still another purpose of the present invention to provide a new and improved cold cathode electron emitter in which dielectric and, hence, device breakdown is reduced.
It is yet another purpose of the present invention to provide a new and improved cold cathode electron emitter in which electron injection into surrounding dielectrics is reduced or eliminated.
It is a further purpose of the present invention to provide a new and improved cold cathode electron emitter with improved operating characteristics and efficiency.